In conventional distributed data processing systems, if a first terminal requires data stored in a second terminal, the first terminal requests the data and the second terminal transmits the data to the first terminal so that the first terminal can process the data. The transmission of raw data which is typically higher in volume than processed data requires a high capacity communication network and limits the number of terminals which can be connected together before significantly reducing overall throughput of the system.
Large distributed processing systems contain a large number of terminals, each having its own computer system. When changes are made to the operation of the distributed processing system, the computer system at each terminal must be updated. Most conventional distributed processing systems do not have the capability to update the operating system of the computer systems at the terminals via the communication network.
In computer systems using object oriented architecture, abstracted data (instance) and a program (method) specifying processing of the data are together treated as an object. Data processing is carried out by processing the methods in such objects and communicating messages therebetween. In object oriented processing, wherever the data is located, procedures for processing the data will be located also. Execution of these procedures is triggered by message transfer between objects, including the transmission of resulting data in messages after processing of data in an object is completed.
Applying object oriented techniques to a distributed data processing system is not easily accomplished due to the need to maintain the linkage between data and method of an object, to determine where an object is located and to communicate between objects. One way of implementing object oriented techniques in a distributed processing system is to maintain a database in each terminal of the objects in all of the terminals. In a large system, this requires a large amount of overhead due to the size of the memory required and the time and communication traffic required to update the object location database in each of the terminals.
An object of the present invention is to provide object oriented processing in all terminals of a distributed processing system, executed as if in a single processing system.
Another object of the present invention is to provide a system for distributed data processing in which objects can be obtained by one terminal from another terminal without maintaining an object location database in all terminals.
A further object of the present invention is to provide a distributed processing system capable of transmitting changes to the operating system programs of the distributed processing system to the terminals via the communication network of the distributed processing system.
Yet another object of the present invention is to provide a method for linking objects regardless of their location or content.